William Thompson (1824-1907), later Lord Kelvin, was the foremost scientific figure of an age that saw the quest of classical physics concluded and marked the beginning of the modern era of atomic physics and relativity. Kelvin's role in the 19th-century scientific revolution can be compared with Newton's position in the 17th century and Einstein's in the 20th. Kelvin meets no simple definition of scientist-engineer. The reader of his biography will be introduced to an extraordinary figure of a past era who in no way fits the image of the modern specialist. It is just this characteristic of Kelvin's life that will take readers, scientists and nonscientists, into the wider universe of technological innovation derived from scientific theory. Kelvin's ideas are expressed in words, not in the language of mathematics.Kelvin directly influenced James Clerk Maxwell, whose work culminated in the electromagnetic theory of light, the theory that ushered in the modern period of electrical science and technology. Kelvin's work on the Atlantic cable shortened the space between Europe and America from weeks to seconds. His controversy with the Darwinians resulted in one of the few scientific debates that the Victorian public followed.Kelvin was the nonpareil scientist of the 19th century, and his biography encompasses the dynamic scientific changes of the Victorian age.